Summary This project seeks to elucidate the mechanistic underpinnings of aversive experiences that arise from choosing between conflicting alternatives. Choice conflict/uncertainty can induce stress as the value and number of one's options increase, and these stressful experiences can persist after a choice is made, as the individual weighs counterfactual choices. Indecisiveness and intolerance of uncertainty also constitute important transdiagnostic factors in Obsessive-Compulsive Disorder (OCD) and Generalized Anxiety Disorder (GAD), disorders that will affect more than 1 in 20 Americans over their lifetimes. However, the basis for stressful experiences of choice conflict, and what their potential may be for negatively impacting ongoing cognition, are still poorly understood. We aim to ground conflict-related neural signals and their subjective sequelae (increased anxiety and decreased choice confidence) in terms of the evidence accumulated for different choice options before and after a decision, measured using fMRI and EEG while human participants choose between salient rewards. In order to better understand cognitive impairments that result from heightened uncertainty and worry, we will further test whether choice conflict signals interfere with ongoing cognition (as evidenced by behavioral and neural measures during a concurrent working memory task); whether this interference is enhanced with increasing trait anxiety and diminished by targeted decision strategies; and what patterns of neural connectivity give rise to the interference. Providing a more complete account of choice conflict in terms of ongoing processes of evidence accumulation will lay the groundwork for understanding varieties of choice paralysis. Furthermore, these efforts will contribute directly to our understanding of neural circuits whose dysregulation exacerbates negative experiences of choice conflict, providing a transdiagnostic mechanism for GAD, OCD, and related disorders. By focusing on the common dysfunctions in neural circuit computations across these disorders, this project aligns well with the criteria of the RDoC initiative, and with its goal of offering potential mechanistic targets for diagnosis and risk assessment. Such contributions will in turn inform approaches to pharmacological and therapeutic intervention aimed at reducing maladaptive responses to everyday occurrences of decision conflict in individuals with these disorders.